1. Field of the Invention
The present invention relates to a switching power supply device; and, more particularly, to a switching power supply device using a current sharing transformer.
2. Description of the Related Art
Recently, functions of electronic and electric equipment or the like required by consumers have been increased, and thus the electronic and electric equipment has been more digitized with using a microcomputer and a processor. Therefore, a power supply device with a small size and high efficiency in each product has been urgently required for service to satisfy various needs of the consumers. In general, a switching power supply device reducing a manufacturing cost and widely used as a basic circuit type of the power supply device uses a switching type, thereby reducing occurrence of loss and being downsized.
In general, because the switching power supply device converts much power with supplying a stable voltage, power loss is inevitably generated. Because most of the loss generated inside is discharged as heat and when power conversion efficiency is reduced, heat generation is increased in proportion to the reduced power conversion efficiency to sometimes shorten a lifetime of a product. Further, in the case of a high-capacitive power supply device used in a midsize and large computer used for server or high-speed operation and large-scale information processing, a size of the power supply device as well as the power conversion efficiency are limited and therefore a design and a manufacturing method to reduce volume and weight in a product development stage have been urgently needed.
A value as a result of dividing a power capacity by a volume of a power supply device product is generally referred to as a power density. That the power density is high means that the product has more power capacity in comparison with an external size thereof and a possibility to make a system smaller is higher. Generally, there are largely three methods to increase the power density. Firstly, it is a method to increase a switching frequency. When increasing the switching frequency, sizes of elements sensitive to the frequency are varied. It is possible to downsize power storage elements such as a transformer and a capacitor because burden on energy storage is reduced when the frequency is increased, thus making the product smaller. Secondary, it is another method to improve the power conversion efficiency. When the power conversion efficiency is increased, an amount of heat generation is reduced and then a size of a heat sink or a conductor is reduced to downsize the power supply device. Lastly, it is still another method to use a construction method and an optimal arrangement technique of the product. To configure and arrange hundreds of elements used in the power supply device in an optimal state is closely related to the downsizing and the reliability of the product and particularly, the configuration and the arrangement of elements utilizing magnetic cores such as a transformer and an inductor give rise to a very important result